Renewable electric fuse



vF. C. LAMAR AND P. J. HOPKINS.4

j RENEWABLE ELECRlC FUSE.

APPLICATION FILED luNE 20.19'18.

1,318,886 A Patented oct. 14,1919.

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Y port the or binding its insrrEio STATES PATENT oEEioE.

FRANK C. LA MAR AND PETER JHOPKIN S, OF PITTSBURGH, PENNSYLVANIA.

RENEWABLE ELECTRC FUSE.

Application led .Tune 20, 1918.

To all 2li/wm t may concern.'

Be it known that we,-FRANK C. LA MAR and PETER HOPKINS, citizens of the United States, residing at Pittsburgh, in the county of Allegheny and State of Pennsylvania, have invented new and useful Improvements in Renewable Electric Fuses, of which the following is a specification.

This invention relates to inclosed or cartridge'fuses of the renewable or refillable type, wherein the fusible elementv or strip is removably mounted in a easing or shell, so that when the fusible element is blown out or disrupted by an excess or overload current, the disrupted or otherwise defective fuse may be removed and replaced by another.

The object of the invention \is to provide a fuse of this type of improved, simple and economical construction, 'and which is easily and readily renewed, and which will effectively withstand the force and effects of the explosion and products of combustion which take place within the shell or casing when the fuse is blown or burnt out.

The invention consists inv a fuse comprising a shell or casing of fiber or other suitable substantially refractory andv insulating material, having external screwthreads upon its ends, washers fitted in the ends of the shell or easing and adapted tohold and supfusible element in proper position within the shell or casing, and internally threaded end caps fittedon the ends of the shell or casing and engaging the ends of the fusible element and firmly holding ends against the washers to secure good contact between the parts, and in the details of construction, combination and arrangement of parts, as we will proceed now more particularly to set forth and finally claim.

In the accompanying drawings, in the several figures of which like parts are similarly designated, Figure l is a side elevation of the fuse assembled and ready for use.I Fig. 2 is a longitudinal sec-tion. on a larger scale, the fuse element being shown in full lines. Fig. 3 isa horizontal section, taken substantially in the plane of the line 3 3, Fig. 2, and at right angles to the section of said figure, and looking in the direction of the arrows. Fig. 4 is a vertical transverse section, taken substantially in the plane of line 4-l, Fig. :2, and looking in Specification of Letters Patent.

all substantially` Patented Oct. 14, 1919. Serial No. 240,892.

provided with a pressure screw for eff'ecting additional pressure upon the ends of the fuse element and maintaining contact between the fuse element and washers.

As shown in the drawings, the shell or casing comprises the 'body portion l, of tubular form, which may be constructed of fiber or any other suitable hard substantially refractory and insulating material, and having its ends reduced at 2, to form shoulders 3. Upon the reduced ends of the shell or casing are fitted metal ferrules 4, and as herein shown, these ferrules are constructed of a section of straight metal tubing preferably brass, of an internal diameter sufficient to fit snuglyupon the reduced ends of the body portion l, with its inner end abutting against the shoulder 3, and of such length that its outer end projects beyond or overhangs the ends of the body portion to afford seats 5 within the -ferrules for fuse element anchoring washers to be described. The said ferrules 4 are provided externally on their inner ends with screwthreads 6, which for the purpose of this invention extend only to about the center of the ferrule. In assembling these parts, the ferrules 4 are fitted or forced upon the reduced ends 2 of the tubular body portion 1 until their threaded ends abut against the shoulders 3, and then the metal of the ferrules just beyond the threads `is rolled or spun downwardly or inwardly into the vfiber of the shell, as shown in Fig. 2, to

form an annular or circumferential groove 7 in the exterior of the ferrule, and to effect a locking of the ferrule upon the end of the body portion against' longitudinal movement or displacement of the ferrules. Pins 8 may be driven through the ferrules and into the fiber of' the shell or tube at any suitable place, as shown in Fig. 2, to prevent rotation of the fer-rules upon the shell.

During the process of rolling the grooves 7 in the ferrule, the outer ends of the ferrules are also slightly reduced to afford a clearance space 9 between the ends 'of the ferrules and the interior of the end caps to be referred to for the escape of gases of combustion from the interior of the shell to the grooves for a purpose as will be hereinafter explained.

Fitted in the seats in the ends of the shell or easing, are fuse element or strip anchoring washers 10, said washers preferably, and as herein shown, being constructed of circular pieces of metal, such as brass, and having a portion of their periphery slabbed of, as at 11, and of such diameterand thickness to fit snugly in the ends of the ferrules 4, with their inner surface engaging the ends of the fiber shell or casing, and their outer surface substantially flush with the ends of the metal ferrules el, the slabbed off portions 11 of the washers il() affording a passage 12 from the interior of the shell for thefuse element 'or strip 13, which may be of any usual or ordinary construction, and as herein shown comprises a at strtip of fusible metal provided with any suitable number, preferably three, readily fusible restricted or reduced blowout portions 14 between its ends, which are adapted to be bent over, as at 15, the slabbed off portions of the washers against the outer surface thereof.

In order to close the ends of the shell or easing, and to effect a good and firm contact between the bent over ends of the fuse element and the washers, caps 16 are provided, said caps being provided with internal threads 1T terminating short of the end wall or head of the cap, and adapted to engage the threads on the ferrules t to secure the caps in place. The end wall or head of the caps 16 is provided with a central hole or perforation 18 to afford a gas opening or escape passage, which as shown lies over the bent ends of the fuse element.

In order to securely lock the end caps upon the ends of the casing or shell against accidental displacement or becoming -loose and disturbing a good electrical contact be tween the parts, the screwthreads on the ferrules 4 and the end caps 16 are constructed ofv gradually increasing pitch from the end of the fuse inwardly, as shown more clearlyin Figs. 2 and 6, so that when the caps are screwed upon the ends of the fuse and are about to reach ytheir inal adjustment, the initial threads of lesser pit-chou the ferrules and caps will be caused to bind, due to the advancing action of the threads of greater pitch, thus effectively locking the end caps in place against accidental displacement or becoming loose from shocks or vibrations or other causes.

As shown in Fig. 7, the end caps 1G may be provided with a setl screw 19, comprising an annular head 2O and a threaded shank 21, the head 20 fitting in a countersunk re cess 22 in the inner wall of the end cap, and the threaded shank 21 engaging a threaded opening through the end cap and exposed upon the outside, and provided with a nick or otherwise constructed to receive an operatingV tool. T he set screw 19 is arranged adjacent to Ithe gas escape opening 19 in the end wall of the cap, or in any other suitable place, so that it will overlie the bent ends of .the fuse element, and after the fuse is assembled, the said set screw may be manipulated or screwed inward against the ends of the fuse element and thus afford additional pressure upon the parts to effect and maintain a good contact therebetween, and furthermore, the set screw 19 also serves by its outward pressure upon the end caps to aid in effecting a binding or locking action between the threads of the ferrules and end caps.

In assembling the fuse, the operator takes the fuse element, which as hereinbefore stated, comprises a thin fiat strip of fusible metal, and positions one of its ends over the slabbed off portion of one ofthe washers and bends the end of the strip down upon the outer face of the washer, and then passes the free end of the strip through the shell or casing and places the washer with the fuse bent thereon into the seat in the end of the shell, the opposite end of the fuse element projecting from the other end of the shell. The operator then places another slabbed off washer in the other end of the shell, with the fuse strip projecting over the slabbed off portion of the washer, care being taken that the slabbed olf portion of the last inserted washer is arranged in a position diametrically opposite the slabbed off por-v tion of the Washer inserted in the other end of the shell, and the other end of the fuse element bent down upon the outer face of j the washer'. reversely to the bend of the other end thereof, thus securing an oblique or diagonal arrangement of the fuse element in the shell, as is common in this type of fuse, and as shown in Fig. 2 of the drawings. The end caps are then placed upon the shell and screwed to place, the end walls of the caps engaging the bent ends of the fuse element and forcing them against the washers, and with a little pressure the threads of varying pitch will effectively lock the end caps against accidental displacement and becoming loose, and thus maintaining and securing the parts in good electrical contact.

In the modification shown in Fig. 7, the fuse is similar to that above described and in addition the end caps are provided with the set screws 19, and after the fuse is assembledvas above described, the said set screws may be engaged by a proper tool and turned to force their heads 20 into contact with the bent ends of the fuse element, to thereby assist in maintaining a perfect contact between the fuse element and the washers, and also exert a back pressure on the end caps and thereby assist in effecting a locking engagement of the threads on the ferrules and end caps.

By this construction, when the fuse is blownA or disrupted by an excess or overload current, the fuse element becomes separated, and the confined gases within the shell gradually escapeofrom the interior of the shell, some of the gas finding its way into the annular grooves 7 in the ferrulesv 4f, which affords an expansion chamber therefor, and eventually leaks out through the `screwthreads until the pressure is reduced and the shell free of the gases.v By thus freeing the shell of the gases, and by the construction herein, little or no damage is done to the shell bythe explosion or the resultant gases and products of combustion, thus enhancing the life of the casing or shell and its appurtenances, it being only necessary to recharge the fuse with a new fuse strip lor element'.

When the fuse has been disrupted or blown out, and it is desired to renew or refill it, the operator` simply removes the end caps by turning them with his thumb and fingers, without the use of tools or other appliances, and without the necessity of removing screws or other fastening devices, and then removing the washers and the damaged fuse strip, and the fuse is then ready for reassembling or refilling' witha new fuse element or strip, as in the assembling of the device as hereinbefore described, andwithout any considerabletrouble or delay, so that lthe line in which the fuse was employed will not be kept out of service any considerable length of time.

117e wish to be understood as notlimiting the invention to the eXact details of construction here-in shown and described, as the same may be changed in various ways, and l still be within the scope of the appended claims.

Vhat we claim is:

1. An electric fuse, comprising a tubular body portion, metallic externally screwthreaded open-ended ferrules fitted on the ends of said body portion and having their outer ends projecting beyond the ends of the body portion to form seats thereon within the ferrules, independent, washers adapted to be fitted in the ends of said ferrules and engaging said seats and adapted to removably anchor a fuse element in said body portion, and internally screwthreaded end caps adapted to be screwed upon said ferrules and engage the ends of the fuse strip to hold them in contact with the anchoring washers and to hold said washers in place.

2. .An 'electric fuse, comprising a casing having circumferential grooves near its ends, means for supporting afuse element in said casing engaging the ends thereof. and end caps fitted upon the ends of the casing and inclosing said rooves, said grooves affording a gas cham er wit-hin the end caps.

3. An electric fuse, comprising a casing having external screwthreads ,near its ends, and circumferential grooves in said casing between said screwthreads and the ends of the casing, .means for supporting a fuse element within the casing engaging the ends of the casing, and internally screwthreaded caps adapted to be screwed upon the ends of the casing to hold the fuse element supporting means in place, the said grooves affording gas chambers within said end caps.

4. An electric fuse, comprising a casing,

. metallic externally screwthreaded ferrules fitted upon the ends of said casing and having a circumferential groove formed therein, means for supporting a fuse element in said casing, and internally screwthreaded caps adapted to be screwed upon the fer-` rules to hold the fuse element supporting means in place, the said groove affording a gas chamber within the end caps.

5. An electric fuse, comprising a easing of insulating material, metallic ferrules, having external screwthreads on their inner ends, fitted on the ends of said casing, and having a circumferential groove formed therein between said threads and their outer ends, means for supporting a fuse element n in sai( casing engaging the ends of the casing, and internally screwthreaded caps adapted to be screwed upon said ferrules to hold the fuse element supporting means in place, the grooves in said ferrules affording gas chambers within the end caps.

6. An electric fuse, comprising a casing of insulating material, metal-lic ferrules having external screwthreads on their inner ends fitted on the ends of the casing and projecting' beyond the ends of the casing at their outer ends to form seats in said ferrules, and circumferential grooves in saidi ,ferrules between said threads and the outer ends of the ferrules, washers fitted in the seats in the ends of the casing and Within the ferrules and engaging the ends of the casing and `adapted to removably support a fuse element in said casing, and internally screwthreaded end caps adapted to be screwed upon said ferrules and engage the ends of the fuse element to hold them in lcontact with said washers, the grooves in fitted in the seats in the ends of the ferrules and engaging the ends of said casing and adapted to removably support a fuse element in said casing, and internally screwthreaded end caps adapted to bescrewed upon said ferrules and engge the ends of the fuse ele ment to hold them in contact with the Washers7 the grooves in said errules affording gas chambers Within the end caps.

8. An electric fuse, comprising a casing having screwthreads at its ends, Washers fitted in the ends of the casing, a fuse strip arranged in said casing and having its ends projecting beyond said Washers und bent down upon the outer face of said Washers,

screwthreaded end ce s adapted to fit upon the screwthreaded en s of the casing and engage the ends of the fuse element to hold said Washers in place, and :t set screw fitted in the head of said end caps and adapted to be forced against the bent ends of the fuse element and exert outward pressure on the end caps, as and for the purpose described. ln testimony whereof, We have hereunto set our handsJ this 15th day of June, 1918.

FRANK C. LA MAR. PETER J. HOPKINS. Witnesses:

N. E. CRITGHLOW, S. P. GORDON, 

